This relates generally to imaging devices, and more particularly, to imaging devices with photodiodes having sub-pixel resolution capabilities.
Image sensors are commonly used in electronic devices such as cellular telephones, cameras, and computers to capture images. In a typical arrangement, an electronic device is provided with an array of image pixels arranged in pixel rows and pixel columns. Circuitry is commonly coupled to each pixel column for reading out image signals from the image pixels. The image pixels contain a single photodiode for generating charge in response to image light.
Conventional imaging systems employ a single image sensor in which the visible light spectrum is sampled by red, green, and blue (RGB) image pixels arranged in a Bayer mosaic pattern. The Bayer Mosaic pattern consists of a repeating cell of two-by-two image pixels, with two green pixels diagonally opposite one another, and the other corners being red and blue.
In certain applications, it may be desirable to capture high-dynamic range images. While highlight and shadow detail may be lost using a conventional image sensor, highlight and shadow detail may be retained using image sensors with high-dynamic-range imaging capabilities.
Common high-dynamic-range (HDR) imaging systems use multiple images that are captured by the image sensor, each image having a different exposure time. Captured short-exposure images may retain highlight detail while captured long-exposure images may retain shadow detail. In a typical device, alternating pairs of rows of pixels capture short and long exposure images to avoid breaking up the Bayer mosaic pattern across exposure times, which can limit the spatial resolution. Performing HDR imaging by generating multiple images captured with different total exposure times for each frame may generate undesirable motion artifacts in the final HDR image.
It would therefore be desirable to be able to provide imaging devices with improved means of generating HDR images.